Water Productivity into Biomass and Energy for 24 Brazilian Sugarcane Varieties Under Drip Irrigation

Abstract

Abstract: The purpose of this study was to evaluate the water productivity (PA) into biomass, sugar and energy for 24 brazilian sugarcane varieties under drip irrigation, subjected to full and deficit irrigation treatments during growing stage. Two experiments were established under greenhouse conditions at the Biosystems Engineering Department, ESALQ/USP, Piracicaba, SP. Experiment 1: ten varieties on a clay soil (RB835054, RB855453, RB855536, RB925211, RB867515, SP89-1115, SP81-3250, CTC14, CTC8 e CTC6) and Experiment 2: fourteen varieties on a sandy-loam soil (RB925345, RB855156, RB966928, RB72454, RB92579, IACSP95-5000, Caiana, SP83-2847, SP90-3414, SP79-1011, CTC17, CTC15, CTC9 e CTC2). In both experiments it was adopted two irrigation treatments: T100 - full irrigation with 100% crop evapotranspiration replacement, maintaining soil moisture near field capacity, and T70 - irrigation with 70% of water depth applied to T100 treatment. Irrigation treatments were initiated at 101 days of crop cycle, corresponding to the end of tillering and the beginning of intense stalk growth phase (first ratoon). It was observed variation in the water productivity into fresh stalk biomass (PABFC) from 16.22 to 29.21 kg m-3, according of the varieties and irrigation treatments applied. The highest values were observed for varieties CTC6, CTC14, RB867515, SP81-3250 and RB92579, under full irrigation treatment (T100), and CTC6, CTC14 and SP90-3414, under deficit irrigation treatment (T70). Water productivity into sugar (PABATR) ranged from 1.95 to 3.84 kg m-3, highest values were observed for varieties CTC6 and RB92579 (T100), as well as RB835054 e RB966928 (T70). Water productivity into total energy (PAETOT) varied from 101.17 to 174.65 MJ m-3, with highest values for varieties:SP81-3250, CTC6, CTC17 and RB92579 (T100 treatment), as well as SP90-3414, SP81-3250 and CTC6 (T70 treatment).